The signaling cascade mediated by D^d-ζ is intact in transfected Jurkat cells. (A) Flow cytometric analysis of D^d and D^d-ζ expression in transfected Jurkat cells. Open histograms represent isotype matched, fluorochrome-labeled control Ab. Closed histograms show staining with anti-CD3 (top panels) or anti-D^d (bottom panels). (B) D^d-ζ–transfected EL4 cells are killed by D^d-specific CTLs. EL4 cells that were untransfected (▪) or transfected with either the MHC-D^d (▴)or D^d-ζ (♦) constructs were used as targets for D^d-specific CTLs in a ⁵¹Cr release cytotoxicity assay. • indicates P815 cells. (C) IL-2 production by D^d-ζ–transfected Jurkat cells following cross-linking with anti-D^d mAb. Following incubation with anti-D^d (34-2-12) or anti-CD3 (OKT3) mAbs, the cells were treated with PMA and cross-linked with plate-bound anti-IgG. Supernatant fluid was tested in a proliferation assay for IL-2 content measuring 3H-thymidine uptake by CTLL-2 cells.